Patients receiving influenza vaccines are currently given one dose every year, except that the first time that the vaccine is given to a child aged 8 years or below they receive two doses separated by at least four weeks.
It is thought (e.g. see ref. 1) that a two-dose regimen will also be required in a pandemic situation, where the human population is immunologically naïve to a new influenza virus strain.
The need for two doses means that, with a fixed supply of antigen, the number of doses that can be made is half of the number that could be made with a one-dose regimen. Thus it has been proposed to use a lower amount of antigen per dose, and to use an adjuvant to compensate for this reduction.
If a one-dose regimen of an adjuvanted vaccine does not elicit a sufficient immune response, however, then a two-dose regimen will be required anyway, with the additional disadvantage that the supply of adequate amounts of adjuvant will also then be an issue. In a situation where hundreds of millions of adjuvanted vaccine doses are being prepared then this issue will be very important, and will be particularly important for synthetic adjuvants.
It is an object of the invention to reduce or avoid this disadvantage.